Microfibers Research Articles

Assessment of Microplastics Distribution in a Biological Wastewater Treatment

Full-scale wastewater treatment facilities are not able to prevent microplastics (MPs) from discharging into natural waters and they are also associated with the land application of the sludge. This study evaluates the distribution of microfibers (MFs) in a lab-scale sequencing batch reactor (SBR) fed by synthetic wastewater (SW) for 93 days. The MFs were analyzed through optical microscopy in the mixed liquor (ML) and the effluent, and sulfuric acid digestion was applied to discriminate between natural and synthetic MFs (i.e., MPs). The results of the optical microscopy analyses were further validated through FTIR spectroscopy. A model describing the evolution over time of the MF concentration in the ML was created, accounting for the MFs entering the system through the SW and atmospheric deposition. The ratio between the MF concentration in the ML and the effluent was 1409 ± 781, demonstrating that MFs settle with the sludge. Consistently, in the ML, 64.9% of the recovered MFs were smaller than 1000 µm (average size 968 µm), while in the effluent, 76.1% of MFs were smaller than 1000 µm (average size 772 µm). Overall, 72% of MFs recovered from the ML were natural fibers and sulfuric acid digestion was successful in eliminating the natural MFs.

Selective solvent extraction and quantification of synthetic microfibers in textile laundry wastewater using pyrolysis-gas chromatography/mass spectrometry

This paper reports a new qualification and quantification method for synthetic microfibers (MFs), polyethylene terephthalate (PET), nylon-6 (N-6), and polyacrylonitrile (PAN), emitted from textiles during the laundering process by applying a sequential process involving the filtration of laundry wastewater, solvent extraction with hexafluoroisopropanol (HFIP), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). After filtering the textile laundry wastewater, selective sampling of synthetic MFs excluding non-target matrices and natural fibers was achieved by extracting the filtered samples with HFIP. MF recovery for HFIP extraction by Py-GC/MS analysis was 91.4 %, 98.5 %, and 98.8 % for PET, N-6, and PAN, respectively. The calibration curves obtained from Py-GC/MS analysis for PET, N-6, and PAN in the weight range between 1 and 50 μg showed good linearity (R2 > 0.994). The detection and quantification limits were lower than 0.2 μg and 0.6 μg for all polymers. The quantification results for the MFs extracted from the textile made from a single filer indicated that PET, N-6, and PAN textile produced 481, 111, and 329 mg of MFs/kg textile, respectively. Compared to the single textile (PET), the blended textiles produced larger amounts of MPs, 961 mg/kg for PET/cotton and 680 mg/kg for PET/wool blended textiles, suggesting the easier formation of MFs from blended textiles during textile laundering.

Hospital cleaning

The aim of this narrative review is to present up-to-date facts concerning hospital cleaning (HC). HC is essential in the prevention of healthcare associated infections (HAI). If a proper HC is followed by a proper use of disinfectants even the HAI caused by the most dangerous nosocomial pathogens like methicillin-resistant Staphylococcus aureus, vancomycin- resistant Enterococcus, carbapenem-resistant Pseudomonas aeruginosa and multidrug-resistant Acinetobacter baumannii may be stopped without closing the ward or placing the patients in isolation. Critical hospital surfaces that may be highly contaminated with pathogens include toilet seats and bowels, toilet flush handles, doorhandles, furniture, hospital equipment, linen, clothes, buttons, switches, computers, printers, shelves, cellphones, curtains, patient chairs, nurse call-buttons and bed rails. Hand-touch sites at bedside pose the highest risk of HAI for patients and these should be targeted with continuous and detail cleaning. The most used methods for the assessment of hospital cleanliness are visual inspection, aerobic colony counts, adenosine triphosphate (ATP) bioluminescence and fluorescent markers. Together with soaps and detergents the environmental-friendly disinfectants like hydrogen peroxide, high-pressure steam, electrolyzed water, ozone, probiotic cleaners and microfiber cloths have a priority in hospital cleaning. Recent advances in the methods of hospital cleaning together with the continuous education of cleaning staff and nurses significantly contribute to the prevention and control of hospital outbreaks.

Chalcogenide Glass Microfibers for Mid-Infrared Optics

With diameters close to the wavelength of the guided light, optical microfibers (MFs) can guide light with tight optical confinement, strong evanescent fields and manageable waveguide dispersion and have been widely investigated in the past decades for a variety of applications. Compared to silica MFs, which are ideal for working in visible and near-infrared regions, chalcogenide glass (ChG) MFs are promising for mid-infrared (mid-IR) optics, owing to their easy fabrication, broad-band transparency and high nonlinearity, and have been attracting increasing attention in applications ranging from near-field coupling and molecular sensing to nonlinear optics. Here, we review this emerging field, mainly based on its progress in the last decade. Starting from the high-temperature taper drawing technique for MF fabrication, we introduce basic mid-IR waveguiding properties of typical ChG MFs made of As2S3 and As2Se3. Then, we focus on ChG-MF-based passive optical devices, including optical couplers, resonators and gratings and active and nonlinear applications of ChG MFs for mid-IR Raman lasers, frequency combs and supercontinuum (SC) generation. MF-based spectroscopy and chemical/biological sensors are also introduced. Finally, we conclude the review with a brief summary and an outlook on future challenges and opportunities of ChG MFs.

From microfibre cloths to poly(vinyl alcohol) hydrogels – conservation cleaning of plastics heritage

In 2012, the EU 7th Framework Programme project Preservation of Plastic Artefacts in Museum Collections (POPART) used optical and scanning electron microscopies, as well as changes in surface energy and gloss to conduct an exhaustive evaluation of cleaning techniques for their effectiveness at cleaning cellulose acetate, polyethylene, poly(vinyl chloride), polystyrene and poly(methyl methacrylate). POPART concluded that applying anionic and nonionic detergent solutions with polyester microfibre cloth cleaned more effectively and produced fewer scratches than using dry, cleaning tools. Polyethylene and polystyrene were the plastics found to be most vulnerable to scratching. In 2018, the Horizon 2020 research project Nanomaterials for the Restoration of Works of Art (NANORESTART) evaluated the effectiveness of hydrogels for cleaning plastics and added infrared spectroscopy to the suite of evaluation instruments used in POPART. The present study compared on an equal basis the materials, model soils and most effective cleaning techniques examined by the POPART and NANORESTART projects. The research concluded that hydrogels induced significantly less damage than traditional cleaning tools and that sebum soil proved more resistant to removal from plastics than carbonaceous soil.

Effects of Tungsten Disulphide Coating on Tapered Microfiber for Relative Humidity Sensing Applications.

Tungsten disulphide (WS2) is a two-dimensional transition-metal dichalcogenide material that can be used to improve the sensitivity of a variety of sensing applications. This study investigated the effect of WS2 coating on tapered region microfiber (MF) for relative humidity (RH) sensing applications. The flame brushing technique was used to taper the standard single-mode fiber (SMF) into three different waist diameter sizes of MF 2, 5, and 10 µm, respectively. The MFs were then coated with WS2 via a facile deposition method called the drop-casting technique. Since the MF had a strong evanescent field that allowed fast near-field interaction between the guided light and the environment, depositing WS2 onto the tapered region produced high humidity sensor sensitivity. The experiments were repeated three times to measure the average transmitted power, presenting repeatability and sensing stability. Each MF sample size was tested with varying humidity levels. Furthermore, the coated and non-coated MF performances were compared in the RH range of 45–90% RH at room temperature. It was found that the WS2 coating on 2 µm MF had a high sensitivity of 0.0861 dB/% RH with linearity over 99%. Thus, MF coated with WS2 encourages enhancement in the evanescent field effect in optical fiber humidity sensor applications.

Adsorption-desorption dynamics of synthetic and naturally weathered microfibers with toxic heavy metals and their ecological risk in an estuarine ecosystem

Microfibers (MFs) in aquatic and marine ecosystems adsorb toxic heavy metals and then transfer the heavy metals enriched MFs to living organisms. In this research paper, the adsorption-desorption dynamics of heavy metals onto MFs was studied by using theoretical models and experimental investigations. The adsorption of metals onto MFs was well correlated for the Freundlich model and the adsorption kinetics follows pseudo-second order rate equation. The adsorption capacity of naturally weathered MFs was 30.8 mg g−1 which is about 35% higher than the synthetic fiber of similar range of size of MFs. The leaching of heavy metals from MFs was found that 90–95% of adsorbed metals were leached within 24 h. The leaching of Ti(II) and Al(III) were slower than the other metal ions. The salinity has shown decrease in adsorption capacity of MFs for heavy metals. Based on the Nemerov pollution index (PN), the naturally weathered MFs enriched with heavy metals in sediments became heavily polluted with PN values between 2.98 and 3.49. The risk index value of 396 represents that the bottom dwellers and other marine organisms in the Narmada estuary high risk from MFs and MFs enriched with metals. This study indicates that MFs play dominant role in fate and distribution of heavy metals in the estuarine ecosystems.

Effects of polyester microfibers (PMFs) and cadmium on lettuce (Lactuca sativa) and the rhizospheric microbial communities: A study involving physio-biochemical properties and metabolomic profiles

Microfibers (MFs) and cadmium (Cd) are widely distributed in soil ecosystems, posing a potential threat to soil biota. To explore potential risks of single MFs and in combination with Cd (co-PMFs/Cd) to soil environment, we systematically investigated the effects of PMFs and co-PMFs/Cd treatments on physio-biochemical performance and metabolomic profile of lettuce (Lactuca sativa), as well as the rhizospheric bacterial communities. Our results showed that both PMFs and co-PMFs/Cd treatments adversely disturbed the plant shoot length, photosynthetic, and chlorophyll content. Co-PMFs/Cd specifically increased the activities of antioxidant enzymes. The metabolites in lettuce leaf were significantly altered by PMFs and co-PMFs/Cd treatments. A significant reduction in the relative abundance of amino acids sugar and sugar alcohols indicated the altered nitrogen and carbohydrates related metabolic pathways. Additionally, PMFs and co-PMFs/Cd treatments altered the structure of rhizospheric bacterial communities and caused significant changes in some key beneficial/functional bacteria involved in the C, and N cycles. The present study provides a novel insight into the potential effects of PMFs on plant and rhizosphere bacterial communities and highlights that PMFs can threaten the terrestrial ecosystem and should be further explored in future research.

Influence of surface material and reprocessing on the durability of antimicrobial surfaces

Abstract The risk of infection from contaminated surfaces has already been shown in several publications. Due to the increased demand for optimized infection control measures during the Corona pandemic, antimicrobial surface technologies have gained more an interest. Apart from many proofs of efficacy, there are only a few studies dealing with the durability of these surface coatings with regard to the material and the reprocessing measures. This work did therefore examine the impact of different materials and surface textures, as well as different detergents and disinfectants, on the durability of antimicrobial surface technologies. Differently structured materials (glass, wood, plastics, metal) and wallpaper bonded to plasterboard were coated with an TiO2Ag based antimicrobial coating (HECOSOL GmbH, Bamberg). These test samples are then used to perform abrasion tests with various cleaning and disinfecting agents and cloth systems (microfiber cloth, cotton cloth, foam cloth). The majority of the test samples in our experimental setup showed at least significant activity. According to our results, both the selection of cleaning and disinfection methods including wiping systems and the surface material have a major impact on the durability of antimicrobial coatings. In order to be able to come to conclusions about the long-term activity of these surface technologies, the effectiveness should be tested not only during the development phase, but also in the finished product and again after several reprocessing cycles in use.

Impact of Chitosan Pretreatment to Reduce Microfibers Released from Synthetic Garments during Laundering

Sewage treatment can remove more than 90% of microplastics, yet large amounts of microplastics are discharged into the ocean. Because microfibers (MFs), primarily generated from the washing of synthetic clothes, are the most abundant type of microplastics among various microplastics detected in the sewage treatment, reducing the amount of MFs entering these treatment plants is necessary. This study aimed to test whether the amount of MFs released from the washing process can be reduced by applying a chitosan pretreatment to the garments before washing. Before the chitosan pretreatment, the polyester clothes released 148 MFs/L, whereas 95% of MFs were reduced after the chitosan pretreatment with 0.7% of chitosan solution. The chitosan pretreatment was applied to other types of garments, such as polyamide and acrylic garments, by treating them with 0.7% of chitosan solution; subsequently, MFs reduced by 48% and 49%, respectively. A morphology analysis conducted after washing revealed that chitosan coating on the polyamide and acrylic were more damaged than on polyester, suggesting that the binding strength of polyamide and acrylic with chitosan was weaker than that of polyester garment. Thus, the results suggested that the chitosan pretreatment might be a promising solution for reducing the amount of MFs generated in the laundering process.

Microplastic and microfiber fluxes in the Seine River: Flood events versus dry periods

Studies on the influence of hydrodynamic conditions on anthropogenic microfiber (MF) and microplastic (MP) distributions in freshwater environments are sparse. In this study, we evaluated the influence of urbanisation gradient on the spatial variability of MFs and MPs. Temporal variability was also assessed by comparing the concentrations and fluxes of MFs and MPs under low flow conditions with those during the January–February 2018 flood event. For each period, Seine river water was collected upstream and downstream of Greater Paris and filtered through an 80 μm net at three different sampling sites. MFs were counted using a stereomicroscope, while MPs were analysed using micro-Fourier transform infrared spectroscopy coupled with siMPle analysis software. The highest concentrations of MFs and MPs were reported at the furthest downstream sites during both periods. However, high water flowrates and urbanisation gradient did not significantly impact MF and MP concentrations, sizes, or polymer distributions. The median MF and MP concentrations were 2.6 and 15.5 items/L and their interquartile ranges were 1.6 and 4.9 items/L (n = 10), respectively, illustrating relatively stable concentrations in spite of the urbanisation gradient and variations in the flowrate. In contrast to the concentration, size, and polymer distribution characteristics, MP mass fluxes were strongly affected by river flow. MF and MP fluxes show increases in the number and mass of particles from upstream to downstream. The downstream site presents high MP mass fluxes, which range between 924 and 1675 tonnes/year. These results may indicate significant MP inputs from the Paris Megacity through wastewater treatment plant effluents and untreated stormwater. The January–February 2018 flood event, which represented 14.5% of the year (in terms of time), contributed 40% of the yearly MP mass fluxes. Thus, flood events contribute strongly to MP fluxes.

Electrostatic flocking of salt-treated microfibers and nanofiber yarns for regenerative engineering.

Electrostatic flocking is a textile technology that employs a Coulombic driving force to launch short fibers from a charging source towards an adhesive-covered substrate, resulting in a dense array of aligned fibers perpendicular to the substrate. However, electrostatic flocking of insulative polymeric fibers remains a challenge due to their insufficient charge accumulation. We report a facile method to flock electrostatically insulative poly(ε-caprolactone) (PCL) microfibers (MFs) and electrospun PCL nanofiber yarns (NFYs) by incorporating NaCl during pre-flock processing. Both MF and NFY were evaluated for flock functionality, mechanical properties, and biological responses. To demonstrate this platform's diverse applications, standalone flocked NFY and MF scaffolds were synthesized and evaluated as scaffold for cell growth. Employing the same methodology, scaffolds made from poly(glycolide-co-l-lactide) (PGLA) (90:10) MFs were evaluated for their wound healing capacity in a diabetic mouse model. Further, a flock-reinforced polydimethylsiloxane (PDMS) disc was fabricated to create an anisotropic artificial vertebral disc (AVD) replacement potentially used as a treatment for lumbar degenerative disc disease. Overall, a salt-based flocking method is described with MFs and NFYs, with wound healing and AVD repair applications presented.

Existence of microplastics in the edible part of the sea cucumber Apostichopus japonicus

Microplastics (MPs; ≤ 5 mm) have become a potential threat to human health due to the widespread detection of MPs in foods consumed by humans. Here, we investigated the potential of MP occurrence in the main edible part of the most valuable species of sea cucumbers (Apostichopus japonicus). Laboratory experiments showed that fluorescent MPs and microfibers (MFs) could transfer into the body wall of the sea cucumber. The evidence revealed that these MPs enter the body wall via the outer surface. Although these MPs decreased after the sea cucumbers were transferred to clean water, traces of MPs (at least one MP particle) were found up to 60 d post-transfer. To validate these laboratory observations, sea cucumber samples were collected from the field. MPs were found in 86% of live and processed sea cucumber samples. The MP abundances in the field samples ranged from 0–15 MPs animal−1 and 0–2 MP g−1. The isolated MPs were mainly MFs, constituting 81% of MPs, followed by fragments, films, and beads. Fourier transform infrared spectroscopy revealed that the polymer composition of the isolated MPs mainly included rayon, followed by polyester and chlorinated polyethylene. The findings of this study demonstrated that the body walls of farmed and processed sea cucumbers contain MPs, thus highlighting the need to control MP pollution during the farming and processing of sea cucumbers.

Low-cost high-performance temperature sensor based on unsymmetrical U-shaped microfiber

A novel temperature sensor based on microfiber (MF) interferometer with low-cost, long-term reliability and high repeatability was developed. The experimental results indicate that the unsymmetrical U-shaped MF has particularly advantages of a thinner waist diameter and better sensing stability compared with symmetrical U-shaped MF in terms of structure and spectrum. The air temperature sensitivity of 10 pm/°C was observed by the sensor with a diameter of 4.26 μm. In order to study the relationship between the structure parameters of transition region and the performance of temperature sensor, we fabricated another MF with a larger taper angle of transition region. The new sensor fabricated with this MF obtained a higher temperature sensitivity of 16.7 pm/°C. Considering the impact force from the temperature measurement environment (such as air and liquid environment), the MF interferometer was packaged in a special glass tube to enhance its impact resistance. After that this proposed sensing structure was applied to the measurement of liquid temperature. Results show that its temperature sensitivity is about 349.5 pm/°C when the liquid temperature changes from 18 °C to 30 °C. The sensor designed in this paper has the advantages of good resistance to liquid impact and high sensitivity. It is of great significance to the application of optical fiber sensor in the detection of liquid and atmospheric environment.

PBAT hollow porous microfibers prepared via electrospinning and their functionalization for potential peptide release

Although microfiber (MF) loaded polypeptides have been widely studied in the field of medicine, load control and slow release remain significant challenges. Herein, polybutylene adipate terephthalate (PBAT) hollow porous MFs (HPMFs) were prepared by improving and regulating the groups and structures of the MFs to address these challenges. The capacity of the HPMFs for the loading of polypeptide can be improved. Measurements involving the use of X-ray photoelectron, energy-dispersive, and ultraviolet (UV) spectroscopies in conjunction with scanning electron microscopy measurements showed that the amount of polypeptide (arginylglycylaspartic acid, RGD) loaded on the HPMFs was significantly higher than that loaded on the MFs. Animal cell experiments revealed that PBAT grafted MAH has good bioactivity. By loading RGD onto HPMFs and MFs, RGD@HPMFs and RGD@MFs were obtained. A study on HeLa and A549 cancer cells showed that the inhibition rates of RGD@HPMFs were higher than that of RGD@MFs by 14.1% and 6.9%, respectively. The results obtained herein show that HPMF scaffold preparation by improving the material groups and regulating the structure of MFs can address the challenges associated with control of the load and sustained release of polypeptides and other drugs.

Tin Disulfide-Coated Microfiber for Humidity Sensing with Fast Response and High Sensitivity

Breath monitoring is significant in assessing human body conditions, such as cardiac and pulmonary symptoms. Optical fiber-based sensors have attracted much attention since they are immune to electromagnetic radiation, thus are safe for patients. Here, a microfiber (MF) humidity sensor is fabricated by coating tin disulfide (SnS2) nanosheets onto the surface of MF. The small diameter (~8 μm) and the long length (~5 mm) of the MF promise strong interaction between guiding light and SnS2. Thus, a small variation in the relative humidity (RH) will lead to a large change in optical transmitted power. A high RH sensitivity of 0.57 dB/%RH is therefore achieved. The response and recovery times are estimated to be 0.08 and 0.28 s, respectively. The high sensitivity and fast response speed enable our SnS2-MF sensor to monitor human breath in real time.

Microplastic Fiber Emissions From Wastewater Effluents: Abundance, Transport Behavior and Exposure Risk for Biota in an Arctic Fjord

Microfibers (MF) are one of the major classes of microplastic found in the marine environment on a global scale. Very little is known about how they move and distribute from point sources such as wastewater effluents into the ocean. We chose Adventfjorden near the settlement of Longyearbyen on the Arctic Svalbard archipelago as a case study to investigate how microfibers emitted with untreated wastewater will distribute in the fjord, both on a spatial and temporal scale. Fiber abundance in the effluent was estimated from wastewater samples taken during two one-week periods in June and September 2017. Large emissions of MFs were detected, similar in scale to a modern WWTP serving 1.3 million people and providing evidence of the importance of untreated wastewater from small settlements as major local sources for MF emissions in the Arctic. Fiber movement and distribution in the fjord mapped using an online-coupled hydrodynamic-drift model (FVCOM-FABM). For parameterizing a wider spectrum of fibers from synthetic to wool, four different density classes of MFs, i.e., buoyant, neutral, sinking, and fast sinking fibers are introduced to the modeling framework. The results clearly show that fiber class has a large impact on the fiber distributions. Light fibers remained in the surface layers and left the fjord quickly with outgoing currents, while heavy fibers mostly sank to the bottom and deposited in the inner parts of the fjord and along the northern shore. A number of accumulation sites were identified within the fjord. The southern shore, in contrast, was much less affected, with low fiber concentrations throughout the modeling period. Fiber distributions were then compared with published pelagic and benthic fauna distributions in different seasons at selected stations around the fjord. The ratios of fibers to organisms showed a very wide range, indicating hot spots of encounter risk for pelagic and benthic biota. This approach, in combination with in-situ ground-truthing, can be instrumental in understanding microplastic pathways and fate in fjord systems and coastal areas and help authorities develop monitoring and mitigation strategies for microfiber and microplastic pollution in their local waters.

Microplastics and microfibers in urban runoff from a suburban catchment of Greater Paris

Microplastics (MPs) and microfibers (MFs) in stormwater have been poorly investigated. Data on their intra and inter rain events variability over time are still sparse. For the first time, the variability of microlitter concentrations in stormwater has been studied. MF and MP concentrations were investigated in stormwater runoff at the outlet of the suburban catchment at Sucy-en-Brie (a suburb of Paris, France), during four rain events. Median MF and MP concentrations were 1.9 and 29 items/L, with an interquartile range of 2.3 and 36 items/L, respectively (N = 18). A different pattern was observed between MFs and MPs. While no relationship or trends were observed for MFs, the highest MP concentrations were observed before the flow rate peak of the rain events. This could indicate a difference in the behaviour between MFs and MPs. We estimated the median MP mass concentration to be 56 μg/L with an interquartile range of 194 μg/L, whereas the mass concentration of macroplastics was estimated to be 31 μg/L with an interquartile range of 22 μg/L at the same sampling site, in a previous study. For this sampling site, MPs and macroplastics have the same order of magnitude. This study may have strong implications on microplastic assessment in urban waters.

Mechanism underlying the toxicity of the microplastic fibre transfer in the sea cucumber Apostichopus japonicus

Microscopic plastic particles (0.1 µm–5 mm) are widespread hazardous pollutants, and microfibres (MFs) are their dominant shape in habitats. Previous field and laboratory studies have demonstrated that MFs enter the coelomic fluid of sea cucumbers from the water through the respiratory tree. However, the possible mechanism underlying the toxicity of this process is not well understood. Herein, RNA-Seq was used to examine the responses of the respiratory tree during the MF transfer process in the sea cucumber Apostichopus japonicus. Polyester synthetic MFs were used, and the number of transferred MFs was controlled to the amount reported from the field. The results showed that the MFs altered gene expression as the transfer process increased. The top genes regulated by MF transfer were mainly related to metabolic processes and signal transduction pathways, with upregulated genes following low MF transfer and downregulated genes following high MF transfer. Functional enrichment analysis revealed the pathways in which differentially expressed genes were enriched under different MF transfer scenarios. The transcriptomic findings were further supported by histological observations, which revealed injury and loss of cell components. This study contributes to understanding the effects of MFs in a valuable echinoderm species through transcriptomic and histological examinations.

Opaque and translucent films from aqueous microfiber suspensions by evaporative self-assembly

Films were prepared by casting microfiber (MF) suspensions on hydrophobic and hydrophilic substrates at controlled conditions (23 °C and 50% relative humidity). It was found that opaque films are formed on the hydrophilic surface, while translucent films are formed on the hydrophobic one. The physical and mechanical properties of the MF films were found to be comparable to those of nano-fibrillated cellulose and microfibrillated cellulose films. The observations from the microfiber film formation on the two substrates of different wettability are discussed in the context of the evaporation of water from sessile droplets containing nanoparticles.